This document summarizes a study that used patient-specific bone geometry and microstructure data from a μCT scan to create a finite element analysis model comparing tibial implant materials. An iterative process was used to determine the representative volume element cube size to capture bone microstructure properties. A tibial implant geometry was meshed and constant loading was applied to model bone stresses. The results found Von Mises stresses in the bone were below yield limits and stresses were slightly lower for a Co-Cr-Mo implant material versus a Ti-Al material, since Co-Cr-Mo is stiffer. The study concluded that numerical modeling can improve implant design and performance through more tailored, patient-specific evaluations under different conditions.

1. Tibial Implant Design Using
Patient Specific Data
www.VIAS3D.com
NO DISCLOSURE IN THIS PRESENTATION
Georgiy Makedonov
Srikanth Srigiriraju, Ph.D.
Arindam Chakraborty, Ph.D.
Arthrex
Claire Henderson, Sr. Product Development Engineer
USA Canada India Mexico

2. Introduction
Background
• Using simulation for knee implant design study
• The use of patient specific-specific bone geometry via µCT
• Digital evidence in the form of virtual patients can be used
• Full digital access to all relevant information enabling to make rapid, science-based, informed
decisions.
Challenge:
• Characterization of physical and mechanical properties of multiphase materials like cancellous and
cortical bones
• Modeling efficiency and accuracy

3. Objective
The aim of this study is to create a FEA model to make a relative comparison between two
implant tray materials (Co-Cr-Mo and Ti-Al) at the tibia-implant interface under the constant
loading condition with the help of patient-specific bone microstructure using a representative
volume element (RVE).

4. Construction Microstructure
70-255
grayscale
(selected)
Step 1: Bone Test Data
Bone
Air
Step 3: Material Homogenization using RVE
Step 2: RVE Size Selection
• The patient-specific bone geometry represented
through a cubic volume is reconstructed in
software from Simpleware Ltd. (ScanIP) using
images from a μCT scan.
• The resulting μCT image is converted to
grayscale with the appropriately chosen cut-off
range for further analysis.
• To save processing memory and computational time,
an iterative process of determining the RVE cube size
is done such that the porosity in the cube between two
consecutive sizes of cubes is not very different.
• Several sizes of cubic samples are selected along the
ML and AP directions of trabecular bone and are
compared for porosity.
• The RVE is designed to capture effective structural and
material properties at microscale level which are used as
input parameters for the macroscale.
• The RVE approach performs statistical averaging of the
microstructural features within the given cubic volume by
applying loading from six independent directions
(Micromechanics Plugin).

5. Design Check using RVE
Step 4: Geometry Specification Step 5: Meshing
Ffem
Step 6: Loads and BC Step 7: Results
• Geometry of the implant is provided by the
Arthrex which was used for the analysis
• Geometry construction of the bone was
performed in Abaqus software.
• Meshing of the bone and implant
was performed using tetrahedral
and hexahedral elements.
• Human weight of the person was applied
as the loading condition
• Rotation of the femoral component is
applied about its flexion axis.​
• Fixed and half-symmetry boundary
conditions were applied to the bone.
• The bone is not expected to yield as the
Von Mises stresses are below the yield
limit for trabecular bone
• Von Mises stress distribution along the
surface of the bone with constant loading
using Co-Cr-Mo implant material is slightly
less compared to Ti-Al implant material,
since Co-Cr-Mo is stiffer material.

6. Conclusions
Conclusions:
• Being able to accurately evaluate designs under different conditions leading to more tailored,
patient-specific implants.
• Using numerical modeling, it is possible to improve product performance.

7. Thank You
www.VIAS3D.com
USA Canada India Mexico